-Fix crash at exit due to unnecesary check in command queue, fixes #2034

-Fix memory corruption due to using wrong singleton in multithreaded physics, fixes #2760

2d/rubegoldberg/engine.cfg

@@ -6,5 +6,6 @@ icon="res://icon.png"
 
 [physics_2d]
 
+thread_model=2
 default_gravity=500
 default_density=0.01